Propeller



F. HOFFMAN Aug. 6, 1929.

PROPELLER Filed July 14 1927 INVENTOR. flan} man I I ATTORNEY.

Patented 6, 1929. t

UNITED STATES PATENT OFFICE.

FRANK HOFFMAN, OF DETROIT, MICHIGAN.

PROPELLER.

Application filed July 14,

My invention relates to a new and useful improvement in a propeller adapted for use particularly on boats and hasfor its ob ect the provision of a propeller which may. be utilized in conjunction with compressed air or steam for effecting apropelling of the boat through the water.

It is another object of the invention to reduce the friction of the boat resulting from the contact of the water therewith so as to economize on the consumption of power used for propelling the boat through the water.

Another object of the invention is the provision of a rotary propeller having passages formed therein through which fluid may be projected to impinge against the wallof water rising rearwardly of the boat a and forwardly and at the sides of the boat so as to assist in propelling the boat through the water.

Other objects will appear hereinafter.

The invention consists in the combination and arrangement of parts hereinafter described and claimed.

The invention will be best understood by a reference to the accompanying drawings which form a part of this specification, and in which Fig. 1 is a fragmentary side elevatlonal view of a boat showing the invention applied.

Fig. 2 is a front elevational view of a propeller embodying the invention with a part broken away and a part shown in sectlon.

Fig. 3 is a fragmentary sectional view taken on line 3--3 of Fig. 2.

Fig. 4 is a fragmentary view taken on line iof Fig. 3. v

Fig. 5 is a view similar to Fig. 3 of a modified form of the invention.

As shown in the drawings the invention is adapted for use with a boat 9 adapted vfor being driven through the water and 1927. Serial No. 205,573.

may be forced in the direction indicated by the arrows through the shaft 11 and intothe propeller blades 12 from which it issues through the enlarged opening 14 formed in the. blades so as to impinge against the wall 15 of water which is rearwardly of the boat and which is constantly moved rearwardly of the boat upon rotation of the propeller. This stream of fluid issuing from the propeller will assist the propeller in driving the boat forwardly. Projecting'forwardly of the boat is a propeller shaft 11' upon which a similar sort of propeller is mounted, the opening in the propeller positioned at the forward part of the boat being directed toward the rear of the boat so as to cause the fluid forced therefrom to impinge against the wall 15' of water which is travelling rearwardly of the boat, thus forcing this water away from the sides of the boat and causing less resistance, while at the same time, urging the boat in a forward direction. Formed on the outer Wall of the propeller in registration with the shaft 11 is an outward projection 16 which provides a charm ber 17, the compressed air, steam or other fluid being forced through the shaft 11, striking in the chamber 17, and being thence deflected towardthe openings 14 formed in the blades. As shown in the drawings these openings are flared outwardly so that a. distribution of the fluid forced therefrom over a large area of the water wall is effected. These openings also are inclined diagonally so that when the power ordinarily used to rotate the propeller shaft 11 is shut off and the fluid under pressure is emitted from the propeller blades, it will have a tendency to rotate'the propeller blades in the opposite direction, or at least resist their continued rotation, so that a retarding of the boat may be effected by the continued flow of the fluid frointhe propeller blades after the propellingpower has been shut off.

In Fig. 5 I have shown the shaft 11 communicating with a chamber 17 formed on the propeller blade 12 having the opening 14 formed therein. The hub 13 being inclined to the blades of the propeller shaft, an inclined mounting the shaft 11 is effected.

In this way I have provided a means for assisting the propelling of the boat throu h the water, and provided also a means or checking the speed of the boat, when deof the propeller on sired. The use of the fluid for this purpose is believed to result in an economy in the propelling of the boat and to add to'the efiiciency generally of the operation of the propelling mechanism.

a 1 While 1 have illustrated and described the preferred form of my invention, I do not wish to limit myself to the precise details of structure shown, but desire to avail myself of such variations and modifications as come within the scope of the appended claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In combination, a tubular propeller shaft, a propeller blade mounted on said shaft, the blades thereof being hollow and communicating with the interior of said shaft, each of said blades having an enlarged outlet opening formed therein, said opening being flared outwardly, and a chamber on said blade positioned opposite the end of said shaft, said chamber oommunicating with said shaft'and with each of said blades the body of said blades being inclined forwardly of said shaft.

2. In combination, a tubular propellin shaft; a tubular propeller mounted on sai shaft and communicating therewith, the blades of said propeller being hollow and communicating with the interior of said shaft, each of said blades having an enlarged outlet opening formed therein, said opening being flared outwardly; a conicalshaped projection on the outer face of said propeller to provide at the central portion of said propeller and opposite the end of said sha't a conical-shaped chamber communieating with said blades.

In testimony whereof I have signed the foregoing specification.

FRANK HOFFMAN. 

